Systems and methods for manipulating and/or installing a pedicle screw

ABSTRACT

A nested dilation tube assembly for enabling implantation of a spinal screw assembly into a vertebrae is provided. The dilation tube assembly includes a plurality of dilation tubes. Each dilation tube includes an elongated cylindrical shaft with an outer diameter slightly larger than a preceding dilation tube. After being inserting into a body, the plurality of dilation tubes form a nested, concentric assembly enabling an opening placed in the spinal area and/or vertebrae to be enlarged up to the outer diameter of a last dilation tube. The inner dilation tubes are capable of being removed from outer dilation tubes such that the inner diameter of an inner most remaining dilation tube forms a space for receiving instruments and/or assemblies.

REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. application Ser. No.14/453,058 filed on Aug. 6, 2014 which is a continuation of U.S.application Ser. No. 11/820,312 filed on Jun. 18, 2007, now issued asU.S. Pat. No. 8,834,527, which claims the benefit of U.S. ProvisionalApplication Ser. No. 60/814,406, filed on Jun. 16, 2006, the entirecontents of which are herein incorporated herein by reference.

FIELD OF THE INVENTION

The present invention is generally directed to installing and adjustinga spinal screw assembly and, more specifically, to systems and methodsfor providing an adjustable securement of a fixation rod to or acrossone or more vertebrae.

BACKGROUND OF THE INVENTION

The spinal column is a highly complex system of bones and connectivetissues that provides support for the body and protects the delicatespinal column and nerves. The spinal column includes a series ofvertebrae stacked one atop the other, whereby each vertebral bodyincludes a relatively strong bone portion forming the outside surface ofthe body and a relatively weak bone portion from the center of the body.Situated between each vertebral body is an intervertebral disc formedfrom a non-bony, fibro-cartilage material that provides for cushioningand dampening of compressive forces applied to the spinal column. Thevertebral canal containing the delicate spinal cords and nerves islocated just posterior to the vertebral bodies.

Various types of spinal column disorders are known and include scoliosis(abnormal lateral curvature of the spine), kyphosis (abnormal forwardcurvature of the spine, usually in the thoracic spine), excess lordosis(abnormal backward curvature of the spine, usually in the lumbar spine),spondylolisthesis (forward displacement of the one vertebra overanother, usually in a lumbar or cervical spine) and other disorderscaused by abnormalities, disease or trauma, such as ruptured or slippeddiscs, degenerative disc disease, fractured vertebra, and the like.Patients suffering from such conditions usually experience extreme anddebilitating pain as well as diminished nerve function.

Certain spinal conditions as mentioned above, including a fracture of avertebrae and a herniated disc, indicate treatment by spinalimmobilization. Several methods of spinal joint immobilization areknown, including surgical fusion and the attachment of pins and boneplates to the affected vertebras.

In an attempt to effectively treat the above-described conditions and,in most cases to relieve pain suffered by the patient, there have beennumerous spinal fixation techniques developed to remedy such issues.Nonetheless, as will be set forth in more detail below, there are somedisadvantages associated with current fixation techniques and devices.U.S. Pat. No. 6,030,388 (granted Feb. 29, 2000 to Yoshimi, et al.)discusses prosthetic devices used in bone fixation systems, such asthose used to treat degenerative and trauma related spinal deformities.This patent discusses a bone fixation element, a linking member and acoupling member having a first channel for receiving a portion of thebone fixation element and a second channel for receiving a portion ofthe linking member. The channels are oriented within the coupling membersuch that the central longitudinal axes of the first and second channelsare offset with respect to one another. Furthermore, the first andsecond channels are configured within the coupling member so as toprovide for communication of a securing force between the bone fixationelement and the linking member such that the bone fixation element isrigidly secured with respect to the linking member.

U.S. Publication No. 2005/0131408 (granted on Jun. 16, 2005 to Sicvol,Christopher W., et al.) discusses delivery and implantation of boneanchors into bone, in particular, one or more vertebral bodies of thespine. This patent discusses a bone anchor having a distal bone engagingportion and a receiving member having a recess for receiving a spinalfixation element. The proximal end of the receiving member may have anarcuate groove formed on an exterior surface thereof to facilitateconnection of an instrument to the receiving member.

U.S. Pat. No. 6,802,844 (granted on Oct. 12, 2004 to Ferree) discussesbodies which connect to vertebra to be aligned, and elongated elementsthat connect to the bodies, which are adjustable relative to the bodiesin multiple dimensions. The patent further discusses locking mechanismsthat allow the alignment to proceed in an orderly fashion until adesired degree of correction is achieved. Each elongated element has ashaped end terminating in the first portion of the lockable couplingmechanism. The vertebral connector bodies each include a feature forattaching the body to respective vertebrae, and the second portion ofthe lockable coupling mechanism.

U.S. Pat. No. 5,772,661 (granted on Jun. 30, 1998 to Michelson)discusses a method and instrumentation for performing spinal surgery,including discectomy, interbody fusion and rigid internal fixation ofthe spine, from the lateral aspect of the spine. This patent discusses asurgical procedure consisting of the removal of spinal material acrossthe disc, fusion, and rigid internal stabilization via the implant mayall be performed via the closed space within the extended outer sleeve.

Thus, it is desirable to provide improved systems for internal fixationof adjacent vertebral bodes of the spine. Accordingly, some embodimentsof the present invention provide an extended range of motion (ascompared to the prior art) for allowing a surgeon additional freedom inlocating the screws and easing the assembly process by reducing therequirements for rod contouring. Such embodiments of the presentinvention minimizes, and in some aspects eliminates, the failures of theprior art, and other problems, by utilizing the structural featuresdescribed herein. Thus, the result is a significantly improved systemand method for manipulating and installing a pedicle screw.

The features and advantages of the invention will be set forth in thedescription which follows, and in part will be apparent from thedescription, or may be learned by the practice of the invention withoutundue experimentation. The features and advantages of the invention maybe realized and obtained by means of the instruments and combinationsparticularly pointed out in the drawings, subsequent detaileddescription and appended claims.

SUMMARY OF THE INVENTION

The foregoing and other features, aspects, and advantages of the presentinvention will be more apparent from the following detailed description,which illustrates exemplary embodiments of the present invention. Someof the embodiments of the present invention relate to a spinal screwassembly for providing an adjustable securement of a stabilization rodbetween at least two vertebrae. The assembly is preferably used with atleast one other such assembly to secure the fixation rod.

In an embodiment of the present invention, a spinal screw assemblyadapted to be secured to a vertebrae is provided. The spinal screwassembly includes a pedicle screw having a head, a threaded shaftportion, and an engagement surface in the head portion for driving thescrew into the vertebrae. The spinal screw assembly also includes a bodymember for receiving the head portion of the screw. The body memberentails a base from which the threaded shaft portion projects, a towerportion, and a pair of opposed slots therein adapted to receive aportion of a fixation rod therebetween. Provided between the base andthe tower portion is a break-away section which allows the tower portionto be removed from the base.

In an embodiment, the spinal screw assembly further details a securablesetscrew for threading onto corresponding threads provided adjacent thepair of opposed slots. The setscrew is adapted to bear against a portionof the fixation rod disposed between the pair of opposed slots to securethe fixation rod within the assembly.

In an embodiment, the spinal screw assembly details at least a portionof the break-away section including threads corresponding to threads ofthe setscrew and threads of the base. The threads of the break-awaysection allows the setscrew to traverse the break-away section into thebase.

In an embodiment of the present invention, a fixation rod is provided.The fixation rod is adapted for securement between at least two spinalscrew assemblies. The fixation rod includes a rod body having apredetermined length and one or more engagement portions provided on atleast one end of the rod.

In an embodiment, the fixation rod further details engagement portionsselected from a group consisting of a depression, an opening, a nib, aprotrusion, a clip, a snap ring, a washer and a flared end. The flareportion includes at least a portion of the perimeter of the end. Also,the nib, protrusion or flared end may be integral with the rod. Theclip, snap ring and/or washer may be received by a groove machined intofixation rod.

In an embodiment of the present invention, a compressor tool forcompressing together at least two vertebrae is provided. The compressortool includes a shaft having a first end for engaging a screw assembly,and a lever having a first end and a second end. The first end of thelever is movably attached to the first end of the shaft and includes anengagement portion for engaging an end of a fixation rod positionedwithin the screw assembly when the lever is in a first position prior tocompression. The compressor also includes a handle attached to the shaftat a second end opposite the first end.

In an embodiment, the compressor tool further details the leverincluding a first portion having a first length and being providedadjacent the first end. The first portion is provided at an anglerelative to the remainder of the length of the lever. The lever ismovably attached to the shaft at a point where the angle of the firstportion begins relative to the remainder of the length of the lever.

In an embodiment of the present invention, a nested dilation tubeassembly for enabling implantation of a spinal screw assembly into avertebrae is provided. The dilation assembly includes a plurality ofdilation tubes of increasing diameter. Each dilation tube includes anelongated cylindrical shaft with an outer diameter slightly larger thana preceding dilation tube. After being inserting into a body, theplurality of dilation tubes form a nested, concentric assembly enablingan opening placed in the spinal area and/or vertebrae to be enlarged upto the outer diameter of a last dilation tube. The inner dilation tubesare capable of being removed from outer dilation tubes such that theinner diameter of an inner most remaining dilation tube forms a spacefor receiving instruments and/or assemblies for implantation into avertebrae.

In an embodiment, the nested dilation tube assembly further includes awire for forming an initial opening into the spine and/or vertebrae. Theplurality of nested dilation tubes fit over the wire and enable anopening in the spine formed by the wire to be enlarged up to the outerdiameter of a last dilation tube.

In an embodiment of the present invention, a spinal screw assemblysystem is provided. The spinal screw assembly system includes a nesteddilation tube assembly for enabling implantation of a spinal screwassembly into a vertebrae. The dilation assembly includes a plurality ofdilation tubes of increasing diameter, each comprising an elongatedcylindrical shaft. Each dilation tube includes an outer diameterslightly larger than a preceding dilation tube. After insertion into abody, the plurality of dilation tubes form a nested, concentric assemblyenabling an opening placed in the spinal area and/or vertebrae to beenlarged up to the outer diameter of a last dilation tube. Innerdilation tubes are capable of being removed from outer dilation tubessuch that the inner diameter of an inner most remaining dilation tubeforms a space for receiving a spinal screw assembly for implantationinto a vertebrae. The system also includes spinal screw assembly isadapted to be secured to a vertebrae, which includes a pedicle screwhaving a head, a threaded shaft portion, and an engagement surface inthe head portion for driving the screw into the vertebrae. The spinalscrew assembly further includes a body member for receiving the headportion of the screw. The body member includes a base from which thethreaded shaft portion projects, a tower portion, a pair of opposedslots therein adapted to receive a portion of a fixation rodtherebetween. A break-away section provided between the base and thetower portion allowing the tower portion to be removed from the basesubsequent to installation. A compressor tool for compressing togetherat least two vertebrae is also provided within the system. Thecompressor tool includes a shaft having a first end for engaging thescrew assembly, and a lever having a first end and a second end. Thefirst end being movably attached to the first end of the shaft andincluding an engagement portion for engaging an end of a fixation rodpositioned within the screw assembly when the lever is in a firstposition prior to compression.

Other objectives and advantages of the present invention will becomeobvious to the reader and it is intended that these objectives andadvantages are within the scope of the present invention.

To accomplish the above and related objectives, this invention may beembodied in the form illustrated in the accompanying drawings, attentionbeing called to the fact, however, that the drawings are illustrativeonly, and that changes may be made in the specific constructionillustrated.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, reference is madeto the following description, taken in conjunction with the accompanyingdrawings, in which like reference characters refer to like partsthroughout, and in which:

FIG. 1A is a pedicle screw for the use in a spinal screw assemblyaccording to some embodiments of the present invention.

FIG. 1B illustrates a perspective view of a spinal screw assembly andits components according to an embodiment of the present invention.

FIG. 1C illustrates a fragmented perspective view of the spinal screwassembly and its components according to an embodiment of the presentinvention.

FIGS. 1D-F are fragmented perspective views of the spinal screw assemblyaccording to an embodiment of the present invention.

FIG. 2 illustrates a perspective view of a plurality of polyaxial screwassemblies according to an embodiment of the present invention, with arod traversing therethrough.

FIG. 3 is a perspective view of a plurality of polyaxial screwassemblies according to an embodiment of the present invention, with arod having traversed therethrough.

FIGS. 4A-C illustrate extruded features at ends of the fixation rod inaccordance with some embodiments of the present invention.

FIGS. 5A-E illustrate the features and assembly according to a dilationinstrument according to some embodiments of the present invention.

FIGS. 6A-C illustrate the features and assembly according to acompression instrument according to some embodiments of the presentinvention

DETAILED DESCRIPTION

It is noted that in this disclosure and particularly in the claimsand/or paragraphs, terms such as “comprises,” “comprised,” “comprising,”and the like can have the meaning attributed to it in U.S. patent law;that is, they can mean “includes,” “included,” “including,” and thelike, and allow for elements not explicitly recited. These and otherembodiments are disclosed or are apparent from and encompassed by, thefollowing description.

In this respect, before explaining at least one embodiment of theinvention in detail, it is to be understood that the invention is notlimited in its application to the details of construction and to thearrangements of the components set forth in the following description orillustrated in the drawings. The invention is capable of otherembodiments and of being practiced and carried out in various ways whereparticular configurations, process steps, and materials disclosed hereinas such configurations, process steps, and materials may vary somewhat.In addition, it is to be understood that the phraseology and terminologyemployed herein are for the purpose of the description and should not beregarded as limiting. Furthermore, as will be apparent to those skilledin the art, the present invention may be embodied in other specificforms without departing from the essential characteristics thereof.

For purposes of the description of the drawings and the embodiments ofthe present invention, as mentioned for each drawing, each figure maynot drawn to scale. Some areas drawn may be bigger and/or simpler inorder to clearly portray the improvement to what has already beenestablished. It will nevertheless be understood that no limitation ofthe scope of the invention is thereby intended. Any alterations andfurther modifications of the inventive features illustrated herein, andany additional applications of the principles of the invention asillustrated herein, which would normally occur to one skilled in therelevant art and having possession of this disclosure, are to beconsidered within the scope of the invention claimed. It is also to beunderstood that the terminology employed herein is used for the purposeof describing particular embodiments only and is not intended to belimiting since the scope of the present invention will be limited onlyby the appended claims and equivalents thereof.

Referring now in detail to the drawings, the spinal screw assembly 100of the present invention comprises a pedicle screw 102, a body member104, a bushing 114 and a setscrew 302 for providing an adjustablesecurement of a stabilization rod 202 between at least two vertebrae(not shown). The spinal screw assembly 100 is used with at least oneother such assembly to secure the fixation rod 202. The presentinvention allows a pedicle screw 102 to be implanted in a minimallyinvasive or percutaneous method.

FIGS. 1A-F illustrate perspective views of a spinal screw assembly 100and its components according to an embodiment of the present invention.FIG. 1A details the pedicle screw 102 which is employed in the assembly100. The pedicle screw 102 is a canulated screw (polyaxial or otherwise)design for the purpose of fusing the thoracolumbar spine. The screw 102is typically intended to canulate the pedicle, be supplemented by a rod202 construct, and held in place with a setscrew 302, also referred toas top loaded setscrew, as described below. Pedicle screw 102 is apolyaxial pedicle screw, which typically includes a spherical headportion 105, a threaded shaft portion 103 and an engagement surface 107in the head portion 105 for use in driving the screw 102 into vertebrae(not shown).

FIG. 1B details the interaction between the screw 102 and body member104 of the spine screw assembly 100. The body member 104 includes a hightop or tower portion 106, base body 108, break zone 110, threads 116,bushing 114, a pair of opposed parallel slots 130 and additionalfeatures 119 for attachment of supplemental devices, as described below.The tower 106 may enable a fully seated (i.e., implanted) screw 102 tobe manipulated or aligned, in multiple directions. In particular, thetower 106 allows such functionality from outside the wound (not shown).The tower 106 is constructed preferably of a breakable web of material,which allows the tower 106 to be easily removed (e.g., the web ofmaterials are broken) from the body member 104 at the break zone 110.The break zone 110 is included at the transition of the tower 106 andthe base body 108. The top tower 106 acts as a break-away section inthat, once the screw 102 has been fully assembled, in which the spinescrew assembly is locked via the setscrew 302, the top portion 106 isremoved or broken off. In a preferred embodiment, after the tower 106has been removed, or broken off, the assembly 100 sit flush with thewound, where no protruding components remain outside of the wound.Alternatively, the components could remain below the wound as well,which is understood by one of ordinary skill in the art.

The tower 106 may be threaded 116, in which the thread 116 is clocked intime to the threaded shaft 103 of the screw 102. Using a continuousthread allows for the setscrew 302 to reduce a rod 202 from tower 106 tothe base body 108 for stabilization of a fixation rod 202. The tower 106further includes an open top 118 to aid in visualization and allowuninterrupted access down the body member 104.

FIG. 1C illustrates a fragmented perspective view of the spinal screwassembly and its components according to an embodiment of the presentinvention. This fragmented view shows that the threaded transition 116exists between the transition of the tower 106 and the base 108 throughthe break zone 110. The threaded transition 116 that exists between thetower 106, base 108 and break zone 110 correspond to threads 304 of thesetscrew 302. The threads 116 of the break-away section 110 allow thesetscrew 302 to traverse the break-away section 110 into the base 106.

Additionally, as discussed below in relation to FIGS. 5A-E, the tower106 includes additional features 119 (e.g., threads) at the top of thetower 106 to attach screwdrivers 504, alignment jigs, and othersupplemental devices to engage the spine screw assembly into vertebrae.

FIGS. 1D-F illustrate the components of the base body 108 of the bodymember 104 where the stabilization of the fixation rod 202 and screw 102occurs. The outer or upper interior surface of side walls 122 of thebase body 108 both have radially projecting serrations formed thereindefining the plurality of axially aligned threads 116. The base body 108shows the pair of opposed parallel slots 130 axially disposed in theside wall 122 thereof, which terminate at their lower ends incurvilinear surfaces 126. The parallel slots 130 are sized to receivethe fixation rod 202 therein, as shown below, with the walls 124defining the slots 130. The slots 130 extending upwardly beyond thebreak zone 110 up to the distal end of the tower portion 106 may beinclined slightly to provide a slight holding force on the rod 202 priorto securing the rod 202 with the setscrew 302. The pair of opposedparallel slots 130 are adapted to receive a portion of the fixation rod202 as a setscrew 302 bears against the fixation rod 202 to releasablysecure the rod 202 within the assembly 100, as described below.Alternatively, a surgeon may exert a slight downward force on the rod202, snapping the rod 202 into the transverse channel defined by thealigned slots 130.

The head portion 106 of the screw 102 is typically positioned in a bodymember 104 adjacent a curvilinear surface 126 disposed about an aperture109 in the end of the base body 106, such that the threaded shaftportion 103 of the screw 102 extends therethrough and the curvilinearinner surface 126 abuts and mates with the head portion 105 of the screw102 so as to define a ball joint therewith. The rounded head surface ofthe head portion 105 rests upon and mates with a rounded interiorsurface formed in the inner or lower end of the base body so as to forma modified ball joint that provides the desired variable angularmovement of the body member with respect to an embedded pedicle screw102. The threaded shaft portion 103 of screw 102 extends therefromthrough the opening 112 in the lower end of base body 108, as picturedin FIG. 1F.

A bushing 114 is preferably employed within the base body 108 adjacentto the side walls 122 to better distribute the longitudinal forcesexerted on the pedicle screw 102; thereby the bushing 114 provides aseat for the fixation rod 202. The bushing 114 further providesflexibility therein and may provide tapered end surfaces adapted to abutopposed sides of the head portion 105. The bushing 114 is positionedwithin the base body 108 of the body member 104 and outwardly adjacentto the head portion 105 of said screw 102. The bushing 114 further abutsthe head portion 105 of the screw 102 upon the setscrew 302 pressingagainst a portion of the fixation rod 202 whereby the force exerted onthe head portion 105 is distributed about the head portion 105.

To provide a basic stability to the system during initial assembly, thebushing 114 can be configured to provide a press fitment about the headportion 105 so that the pedicle screw 102, body member 104 and bushing114 will not move freely prior to the insertion and securement of thefixation rod 202.

In another embodiment of the invention, the bushing 114 may not beemployed. The opposed axial slots 130 in the side wall 122 of the bodymember 104 of the assembly 100 define a seat for the fixation rod 202.When the setscrew 302 is pressed into the body member 104 with thefixation rod 202 extending there across, the planar bottom surface abutsthe fixation rod 202 and, in this instance, presses the rod 202 againstthe upper end of the head portion 105 of the pedicle screw. For suchapplications, the body member 104 and pedicle screw 102 would be sizedsuch that the upper part of the head portion 105 of the screw 102 wouldproject above the bottom of the seat defined by the axially opposedslots 130 so as to enable the rod 202 to press against the screw 102 andcreate a rigid, yet adjustable, securement between the body member 104and the pedicle screw 202.

FIG. 2 illustrates a perspective view of a plurality of polyaxial screwassemblies 100 according to an embodiment of the present invention, witha rod 202 traversing therethrough. The fixation rod 202 enters the bodymember 104 through each pair of slots 130. The fixation rod 202traverses down the body member 104 until it becomes fully seated withinthe parallel slots 130 of each body member 104, as pictured below inrelation to FIG. 3. The fixation rod 202 may traverse each body member104 though force applied by a surgeon, through force applied by asetscrew 302 pushing the rod 202 down the body member or other means,which would be recognized by one with skill in the art.

FIG. 3 is a perspective view of a plurality of polyaxial screwassemblies 100 according to an embodiment of the present invention, witha rod 202 having traversed therethrough. After affixation of the rod 202within the screw assemblies 100, setscrews or setscrews 302 are utilizedto lock the fully seated rod 202 in place within the body member 104.The setscrew 302 includes threads 304 to engage the threaded portion 116of the body member 104. Accordingly, the threaded portion 116 of thebody member may be just a portion of the body member 104 or the entirebody member 104. The interlocked threads 304 of the setscrew 302 mayallow the surgeon to tighten the clamping force on the fixation rod 202by simply pressing downwardly on the setscrew 302. The threads 304 willhold the component parts in place. To adjust or remove the rod 202, thesetscrew 302 is simply rotated 90 degrees about its longitudinal axis,whereupon the threads 304 of the cap 302 are aligned with the open slots130 in the body member 104, allowing the cap 302 to be simply pulledupwardly away from the fixation rod 202. An engagement slot is providedin the top portion of cap 302 to facilitate the rotation of the setscrewwith a suitably sized mating tool (not shown), which is well known inthe art.

FIGS. 4A-C illustrate extruded features at ends of the fixation rod inaccordance with embodiments of the present invention. The fixation rod202 may embody extruded features at the ends of the rod 202. Thesefeatures are configured to receive a corresponding engagement portion ofa compression tool 600 for moving the fixation rod 202 relative to aspinal screw assembly 100 when the spinal screw assembly 100 is affixedto the vertebrae, as discussed below in relation to FIGS. 6A-6C. Asillustrated in FIG. 4A, the fixation rod 202 includes pegs, shortspikes, nibs, washers, or flared portions 402 protruding on the distalends. The flared portions 402 may include at least a portion of theperimeter of the end of the fixation rod 202. In FIG. 4B, the fixationrod 202 includes snap ring clips 404 sitting in grooves, depressions oropenings (not shown) machined into the distal ends at a proximal portionof the rod 202. FIG. 4C depicts the features of FIG. 1, the pegs orshort spikes 402 being machined into the fixation rod 202 as one piece.The above identified machined and extruded features appended to thefixation rod 202 provide the benefits for use by a surgeon. The rod 202is fully contained within the body member 104 by the setscrew 302. Therod 202 also need not be tilted or the body member 104, including thetowers 106, stretched to allow the rod 202 to be placed into a fullyseated position. Furthermore, these above identified features of 402 and404 allow other instruments to interact with the spine screw assembly100, as discussed below in relation to FIGS. 6A-6B, as well as otherembodiments which would be recognized by one skilled in the art.

FIGS. 5A-E illustrate the features and assembly according to a nesteddilation tube assembly 500. FIG. 5A illustrates the components utilizedin the nested dilation tube assembly 500 in accordance with the spinescrew assembly 100. As pictured the screw driver 504 (or any other typeof mating tool) engages the body member 104 atop the tower portion 106via the additional features 119 (e.g., threads). The screw 102 and bodymember 104 enter a dilator 502 (or tube) and thereby engage thevertebrae in accordance with the embodiments of the present invention.As shown in FIG. 5B, the dilation assembly 500 allows the surgeon to usea small wire 501 and progressively dilate the vertebrae (not shown) witha plurality of dilation tubs 502 a-502 d, each of the dilation tubshaving an increasingly greater diameter than the other from the inner tothe outer dilation tube. As shown in FIG. 5C, once the smaller diameterdilator 502 a (referenced also as the inner dilation tube) has beenimplanted, larger diameter dilators 502 b (also referenced as the medialdilation tube) and 502c (also referenced as the outer dilation tube) areimplanted, respectively. Upon increasing the diameter of the dilators502 a-502 c by implanting a dilator 502 with a greater diameter,previously implanted dilators 502 with smaller diameters may be removed,thereby increasing the opening in the vertebrae; hence, once the largesttube 502 c is utilized, the inner dilation tubes 502 a and 502 b can beremoved. The dilation tubes 502 after being inserted into a body form anested, concentric assembly 500 enabling an opening placed in the spinalarea and/or vertebrae to be enlarged up to the outer diameter of a lastdilation tube 502 c. It can be recognized that one skilled in the art,that the smaller diameter tubes 502 may be removed after each increasein diameter, or all together at the end, after the largest diameter tubeis employed. Interior dilation tubes 502 a and 502 b entail a lip areaas flared protrusions 503 a and 503 b from the distal end of each tube.The protrusions 503 a and 503 b allow for removal of each tubeaccordingly. The protrusions 503 a and 503 b also prevent the tubes 502a and 502 b from entering the assembly 500 beyond a predetermined point.It would also be recognized by one of ordinary skill in the art that avariety of number of dilation tubes 502 could be utilized with assembly500. FIG. 5D depicts the components of the tube 502, body member andscrew 102 as discussed above. As illustrated in FIG. 5E, upon employmentof the largest diameter tube 502, the screw assembly 100 is implantedthrough the tube 502 via the use of the screw driver 504.

FIGS. 6A-C illustrate the features and assembly according to acompression embodiment of the present invention. FIG. 6A illustrates thecompressor 600 including a handle 602, body shaft 604 and lever 606. Thelever 606 includes a first end being movably attached to the first endof the shaft 604 and including an engagement portion (not shown) forengaging an end of a fixation rod 202 positioned within the screwassembly when the lever is in a first position prior to compression, anda second end utilized for compression 600. Lever 606 further includes aportion having a first length and being provided adjacent the first end.The first portion is provided at an angle relative to the remainder ofthe length of the lever 606. The lever 606 is movably attached to theshaft 604 at a point where the angle of the first portion beginsrelative to the remainder of the length of the lever 606. The shaft 604connects the handle 602 and the lever 606 and embodies a cylindricalshape adapted to slide over and down the spinal screw assembly 100. Theshaft 604 may entail a substantially tubular shape that allows the shaft604 to receive at least a portion of a screw assembly 100 therein.

FIG. 6B illustrates the compressor 600 including the handle 602 locatedin conjunction with the distal end of the body member 104 atop the towerportion 106 and the lever 606 positioned in conjunction with thefixation rod 202 which is fully seated in the screw assembly 100. Thecompressor 600 is positioned adjacent to the body member 104 and abovethe fixation rod 202, therein the compressor 600 grabs hold of aprotrusion of the fixation rod 202, as discussed above in relation toFIGS. 4A-4C and elements 402 and 404. As illustrated in FIG. 6C, a loadis applied to the fixation rod 202 by manipulating the level 606 of thecompressor 600 and thereby applying a load to the fixation rod 202. Toprovide balance or leverage upon applying the load to the fixation rod202, the surgeon can grip onto the handle 602. The fixation rod 202 isdisplaced within the assembly 100 a distance up to a 5 mm range uponincreasing the applied load by a lever depression 608, whereby thedistance between a screw assemblies is decreased. Once the desiredcompression is achieved, the setscrew 302 is finally tightened upon thefixation rod 202 whereby the displacement and compression are preserved.

As described in FIGS. 5A-E and 6A-C, after dilation and compressionoccurs, it would be understood by one of ordinary skill in the art thatthe tower portion would be broken off, as described above, therebycreating a fully seated and implanted assembly.

While illustrative embodiments of the invention have been describedabove, it is, of course, understood that various modifications will beapparent to those of ordinary skill in the art. Such modifications arewithin the spirit and scope of the invention, which is limited anddefined only by the appended claims.

Although illustrative embodiments of the invention have been describedin detail herein with reference to the accompanying drawings, it is tobe understood that the invention is not limited to those preciseembodiments, and that various changes and modifications can be effectedtherein by one skilled in the art without departing from the scope andspirit of the invention as defined by the appended claims.

We Claim:
 1. A nested dilation tube assembly for opening a surgicalsite, the nested dilation tube assembly comprising: a plurality ofdilation tubes having at least an inner dilation tube, a medial dilationtube and an outer dilation tube, each of the plurality of tubes have anelongated cylindrical shaft with a bore, each of the elongatedcylindrical shaft having an outer diameter, wherein the outer diameterof the outer dilation tube is larger than the outer diameter of themedial dilation tube, and the outer diameter of the medial dilation tubeis larger than the outer diameter of the inner dilation tube so as toallow the plurality of dilation tubes to form a nested, concentricassembly enabling an opening to be enlarged up to the outer diameter ofthe outer dilation tube.
 2. The nested dilation tube assembly as setforth in claim 1, wherein the inner dilation tube is configured to beremoved from the outer dilation tube so as to provide a space forreceiving instruments and/or assemblies for implantation into thesurgical site.
 3. The nested dilation tube assembly of claim 1, furtherincluding a wire, the wire configured to slide within the bore of theinner dilation tube so as to form an initial opening, wherein each ofthe plurality of dilation tubes may be sequentially inserted into thesurgical site so as to progressively enlarge the surgical site.
 4. Thenested dilation tube assembly of claim 1, wherein the inner dilationtube is longer than the medial dilation tube, and the medial dilationtube is longer than the outer dilation tube.
 5. The nested dilation tubeassembly of claim 1, wherein the inner dilation tube includes a firstlip disposed on a proximal end of the inner dilation tube.
 6. The nesteddilation tube assembly of claim 5, wherein the first lip is a flaredprotrusion.
 7. The nested dilation tube assembly of claim 1, wherein themedial dilation tube includes a second lip disposed on a proximal end ofthe medial dilation tube.
 8. The nested dilation tube assembly of claim7, wherein the second lip is a flared protrusion.
 9. The nested dilationtube assembly of claim 1, wherein each of the plurality of dilationtubes a pointed head disposed on a distal end of each of the elongatedcylindrical shaft the a respective one of the plurality of dilationtubes.
 10. The nested dilation tube assembly as set forth in claim 9,wherein the pointed head of the inner dilation tube is narrower than thepointed head of the medial dilation tube, and the pointed head of themedial dilation tube is narrower than the pointed head of the outerdilation tube.
 11. A method of making a surgical opening in a surgicalsite, the method comprising the steps of: providing a plurality ofdilation tubes having at least an inner dilation tube, a medial dilationtube and an outer dilation tube, each of the plurality of tubes have anelongated cylindrical shaft with a bore, each of the elongatedcylindrical shaft having an outer diameter, wherein the outer diameterof the outer dilation tube is larger than the outer diameter of themedial dilation tube, and the outer diameter of the medial dilation tubeis larger than the outer diameter of the inner dilation tube; providinga wire, the wire disposed within the inner dilation tube; inserting thewire into the surgical site; inserting the inner dilation tube into thesurgical site; sliding the medial dilation tube over the inner dilationtube so as to enlarge the surgical site; sliding the outer dilation tubeover the medial dilation tube so as to enlarge the surgical site,wherein the inner dilation tube, the medial dilation tube and the outerdilation tube form a nested, concentric assembly.
 12. The method as setforth in claim 11, further including the following steps in sequence:removing the wire from the surgical site; removing the inner dilationtube from the surgical site; and removing the medial dilation tube fromthe surgical site.
 13. The method as set forth in claim 12, furtherincluding the step of inserting a screw into the surgical site withinthe bore of the elongated cylindrical shaft of the outer dilation tube.